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diff --git a/user_guide_src/source/libraries/image_lib.rst b/user_guide_src/source/libraries/image_lib.rst new file mode 100644 index 000000000..ca464df9c --- /dev/null +++ b/user_guide_src/source/libraries/image_lib.rst @@ -0,0 +1,497 @@ +######################## +Image Manipulation Class +######################## + +CodeIgniter's Image Manipulation class lets you perform the following +actions: + +- Image Resizing +- Thumbnail Creation +- Image Cropping +- Image Rotating +- Image Watermarking + +All three major image libraries are supported: GD/GD2, NetPBM, and +ImageMagick + +.. note:: Watermarking is only available using the GD/GD2 library. In + addition, even though other libraries are supported, GD is required in + order for the script to calculate the image properties. The image + processing, however, will be performed with the library you specify. + +********************** +Initializing the Class +********************** + +Like most other classes in CodeIgniter, the image class is initialized +in your controller using the $this->load->library function:: + + $this->load->library('image_lib'); + +Once the library is loaded it will be ready for use. The image library +object you will use to call all functions is: $this->image_lib + +Processing an Image +=================== + +Regardless of the type of processing you would like to perform +(resizing, cropping, rotation, or watermarking), the general process is +identical. You will set some preferences corresponding to the action you +intend to perform, then call one of four available processing functions. +For example, to create an image thumbnail you'll do this:: + + $config['image_library'] = 'gd2'; $config['source_image'] = '/path/to/image/mypic.jpg'; $config['create_thumb'] = TRUE; $config['maintain_ratio'] = TRUE; $config['width'] = 75; $config['height'] = 50; $this->load->library('image_lib', $config); $this->image_lib->resize(); + +The above code tells the image_resize function to look for an image +called *mypic.jpg* located in the source_image folder, then create a +thumbnail that is 75 X 50 pixels using the GD2 image_library. Since the +maintain_ratio option is enabled, the thumb will be as close to the +target width and height as possible while preserving the original aspect +ratio. The thumbnail will be called *mypic_thumb.jpg* + +.. note:: In order for the image class to be allowed to do any + processing, the folder containing the image files must have write + permissions. + +.. note:: Image processing can require a considerable amount of server + memory for some operations. If you are experiencing out of memory errors + while processing images you may need to limit their maximum size, and/or + adjust PHP memory limits. + +Processing Functions +==================== + +There are four available processing functions: + +- $this->image_lib->resize() +- $this->image_lib->crop() +- $this->image_lib->rotate() +- $this->image_lib->watermark() +- $this->image_lib->clear() + +These functions return boolean TRUE upon success and FALSE for failure. +If they fail you can retrieve the error message using this function:: + + echo $this->image_lib->display_errors(); + +A good practice is use the processing function conditionally, showing an +error upon failure, like this:: + + if ( ! $this->image_lib->resize()) { echo $this->image_lib->display_errors(); } + +Note: You can optionally specify the HTML formatting to be applied to +the errors, by submitting the opening/closing tags in the function, like +this:: + + $this->image_lib->display_errors('<p>', '</p>'); + +Preferences +=========== + +The preferences described below allow you to tailor the image processing +to suit your needs. + +Note that not all preferences are available for every function. For +example, the x/y axis preferences are only available for image cropping. +Likewise, the width and height preferences have no effect on cropping. +The "availability" column indicates which functions support a given +preference. + +Availability Legend: + +- R - Image Resizing +- C - Image Cropping +- X - Image Rotation +- W - Image Watermarking + +Preference +Default Value +Options +Description +Availability +**image_library** +GD2 +GD, GD2, ImageMagick, NetPBM +Sets the image library to be used. +R, C, X, W +**library_path** +None +None +Sets the server path to your ImageMagick or NetPBM library. If you use +either of those libraries you must supply the path. +R, C, X +**source_image** +None +None +Sets the source image name/path. The path must be a relative or absolute +server path, not a URL. +R, C, S, W +**dynamic_output** +FALSE +TRUE/FALSE (boolean) +Determines whether the new image file should be written to disk or +generated dynamically. Note: If you choose the dynamic setting, only one +image can be shown at a time, and it can't be positioned on the page. It +simply outputs the raw image dynamically to your browser, along with +image headers. +R, C, X, W +**quality** +90% +1 - 100% +Sets the quality of the image. The higher the quality the larger the +file size. +R, C, X, W +**new_image** +None +None +Sets the destination image name/path. You'll use this preference when +creating an image copy. The path must be a relative or absolute server +path, not a URL. +R, C, X, W +**width** +None +None +Sets the width you would like the image set to. +R, C +**height** +None +None +Sets the height you would like the image set to. +R, C +**create_thumb** +FALSE +TRUE/FALSE (boolean) +Tells the image processing function to create a thumb. +R +**thumb_marker** +_thumb +None +Specifies the thumbnail indicator. It will be inserted just before the +file extension, so mypic.jpg would become mypic_thumb.jpg +R +**maintain_ratio** +TRUE +TRUE/FALSE (boolean) +Specifies whether to maintain the original aspect ratio when resizing or +use hard values. +R, C +**master_dim** +auto +auto, width, height +Specifies what to use as the master axis when resizing or creating +thumbs. For example, let's say you want to resize an image to 100 X 75 +pixels. If the source image size does not allow perfect resizing to +those dimensions, this setting determines which axis should be used as +the hard value. "auto" sets the axis automatically based on whether the +image is taller then wider, or vice versa. +R +**rotation_angle** +None +90, 180, 270, vrt, hor +Specifies the angle of rotation when rotating images. Note that PHP +rotates counter-clockwise, so a 90 degree rotation to the right must be +specified as 270. +X +**x_axis** +None +None +Sets the X coordinate in pixels for image cropping. For example, a +setting of 30 will crop an image 30 pixels from the left. +C +**y_axis** +None +None +Sets the Y coordinate in pixels for image cropping. For example, a +setting of 30 will crop an image 30 pixels from the top. +C +Setting preferences in a config file +==================================== + +If you prefer not to set preferences using the above method, you can +instead put them into a config file. Simply create a new file called +image_lib.php, add the $config array in that file. Then save the file +in: config/image_lib.php and it will be used automatically. You will +NOT need to use the $this->image_lib->initialize function if you save +your preferences in a config file. + +$this->image_lib->resize() +=========================== + +The image resizing function lets you resize the original image, create a +copy (with or without resizing), or create a thumbnail image. + +For practical purposes there is no difference between creating a copy +and creating a thumbnail except a thumb will have the thumbnail marker +as part of the name (ie, mypic_thumb.jpg). + +All preferences listed in the table above are available for this +function except these three: rotation_angle, x_axis, and y_axis. + +Creating a Thumbnail +-------------------- + +The resizing function will create a thumbnail file (and preserve the +original) if you set this preference to TRUE:: + + $config['create_thumb'] = TRUE; + +This single preference determines whether a thumbnail is created or not. + +Creating a Copy +--------------- + +The resizing function will create a copy of the image file (and preserve +the original) if you set a path and/or a new filename using this +preference:: + + $config['new_image'] = '/path/to/new_image.jpg'; + +Notes regarding this preference: + +- If only the new image name is specified it will be placed in the same + folder as the original +- If only the path is specified, the new image will be placed in the + destination with the same name as the original. +- If both the path and image name are specified it will placed in its + own destination and given the new name. + +Resizing the Original Image +--------------------------- + +If neither of the two preferences listed above (create_thumb, and +new_image) are used, the resizing function will instead target the +original image for processing. + +$this->image_lib->crop() +========================= + +The cropping function works nearly identically to the resizing function +except it requires that you set preferences for the X and Y axis (in +pixels) specifying where to crop, like this:: + + $config['x_axis'] = '100'; $config['y_axis'] = '40'; + +All preferences listed in the table above are available for this +function except these: rotation_angle, width, height, create_thumb, +new_image. + +Here's an example showing how you might crop an image:: + + $config['image_library'] = 'imagemagick'; $config['library_path'] = '/usr/X11R6/bin/'; $config['source_image'] = '/path/to/image/mypic.jpg'; $config['x_axis'] = '100'; $config['y_axis'] = '60'; $this->image_lib->initialize($config); if ( ! $this->image_lib->crop()) { echo $this->image_lib->display_errors(); } + +Note: Without a visual interface it is difficult to crop images, so this +function is not very useful unless you intend to build such an +interface. That's exactly what we did using for the photo gallery module +in ExpressionEngine, the CMS we develop. We added a JavaScript UI that +lets the cropping area be selected. + +$this->image_lib->rotate() +=========================== + +The image rotation function requires that the angle of rotation be set +via its preference:: + + $config['rotation_angle'] = '90'; + +There are 5 rotation options: + +#. 90 - rotates counter-clockwise by 90 degrees. +#. 180 - rotates counter-clockwise by 180 degrees. +#. 270 - rotates counter-clockwise by 270 degrees. +#. hor - flips the image horizontally. +#. vrt - flips the image vertically. + +Here's an example showing how you might rotate an image:: + + $config['image_library'] = 'netpbm'; $config['library_path'] = '/usr/bin/'; $config['source_image'] = '/path/to/image/mypic.jpg'; $config['rotation_angle'] = 'hor'; $this->image_lib->initialize($config); if ( ! $this->image_lib->rotate()) { echo $this->image_lib->display_errors(); } + +$this->image_lib->clear() +========================== + +The clear function resets all of the values used when processing an +image. You will want to call this if you are processing images in a +loop. + +:: + + $this->image_lib->clear(); + + +****************** +Image Watermarking +****************** + +The Watermarking feature requires the GD/GD2 library. + +Two Types of Watermarking +========================= + +There are two types of watermarking that you can use: + +- **Text**: The watermark message will be generating using text, either + with a True Type font that you specify, or using the native text + output that the GD library supports. If you use the True Type version + your GD installation must be compiled with True Type support (most + are, but not all). +- **Overlay**: The watermark message will be generated by overlaying an + image (usually a transparent PNG or GIF) containing your watermark + over the source image. + +Watermarking an Image +===================== + +Just as with the other functions (resizing, cropping, and rotating) the +general process for watermarking involves setting the preferences +corresponding to the action you intend to perform, then calling the +watermark function. Here is an example:: + + $config['source_image'] = '/path/to/image/mypic.jpg'; $config['wm_text'] = 'Copyright 2006 - John Doe'; $config['wm_type'] = 'text'; $config['wm_font_path'] = './system/fonts/texb.ttf'; $config['wm_font_size'] = '16'; $config['wm_font_color'] = 'ffffff'; $config['wm_vrt_alignment'] = 'bottom'; $config['wm_hor_alignment'] = 'center'; $config['wm_padding'] = '20'; $this->image_lib->initialize($config); $this->image_lib->watermark(); + +The above example will use a 16 pixel True Type font to create the text +"Copyright 2006 - John Doe". The watermark will be positioned at the +bottom/center of the image, 20 pixels from the bottom of the image. + +.. note:: In order for the image class to be allowed to do any + processing, the image file must have "write" file permissions. For + example, 777. + +Watermarking Preferences +======================== + +This table shown the preferences that are available for both types of +watermarking (text or overlay) + +Preference +Default Value +Options +Description +**wm_type** +text +text, overlay +Sets the type of watermarking that should be used. +**source_image** +None +None +Sets the source image name/path. The path must be a relative or absolute +server path, not a URL. +**dynamic_output** +FALSE +TRUE/FALSE (boolean) +Determines whether the new image file should be written to disk or +generated dynamically. Note: If you choose the dynamic setting, only one +image can be shown at a time, and it can't be positioned on the page. It +simply outputs the raw image dynamically to your browser, along with +image headers. +**quality** +90% +1 - 100% +Sets the quality of the image. The higher the quality the larger the +file size. +**padding** +None +A number +The amount of padding, set in pixels, that will be applied to the +watermark to set it away from the edge of your images. +**wm_vrt_alignment** +bottom +top, middle, bottom +Sets the vertical alignment for the watermark image. +**wm_hor_alignment** +center +left, center, right +Sets the horizontal alignment for the watermark image. +**wm_hor_offset** +None +None +You may specify a horizontal offset (in pixels) to apply to the +watermark position. The offset normally moves the watermark to the +right, except if you have your alignment set to "right" then your offset +value will move the watermark toward the left of the image. +**wm_vrt_offset** +None +None +You may specify a vertical offset (in pixels) to apply to the watermark +position. The offset normally moves the watermark down, except if you +have your alignment set to "bottom" then your offset value will move the +watermark toward the top of the image. +Text Preferences +---------------- + +This table shown the preferences that are available for the text type of +watermarking. + +Preference +Default Value +Options +Description +**wm_text** +None +None +The text you would like shown as the watermark. Typically this will be a +copyright notice. +**wm_font_path** +None +None +The server path to the True Type Font you would like to use. If you do +not use this option, the native GD font will be used. +**wm_font_size** +16 +None +The size of the text. Note: If you are not using the True Type option +above, the number is set using a range of 1 - 5. Otherwise, you can use +any valid pixel size for the font you're using. +**wm_font_color** +ffffff +None +The font color, specified in hex. Note, you must use the full 6 +character hex value (ie, 993300), rather than the three character +abbreviated version (ie fff). +**wm_shadow_color** +None +None +The color of the drop shadow, specified in hex. If you leave this blank +a drop shadow will not be used. Note, you must use the full 6 character +hex value (ie, 993300), rather than the three character abbreviated +version (ie fff). +**wm_shadow_distance** +3 +None +The distance (in pixels) from the font that the drop shadow should +appear. +Overlay Preferences +------------------- + +This table shown the preferences that are available for the overlay type +of watermarking. + +Preference +Default Value +Options +Description +**wm_overlay_path** +None +None +The server path to the image you wish to use as your watermark. Required +only if you are using the overlay method. +**wm_opacity** +50 +1 - 100 +Image opacity. You may specify the opacity (i.e. transparency) of your +watermark image. This allows the watermark to be faint and not +completely obscure the details from the original image behind it. A 50% +opacity is typical. +**wm_x_transp** +4 +A number +If your watermark image is a PNG or GIF image, you may specify a color +on the image to be "transparent". This setting (along with the next) +will allow you to specify that color. This works by specifying the "X" +and "Y" coordinate pixel (measured from the upper left) within the image +that corresponds to a pixel representative of the color you want to be +transparent. +**wm_y_transp** +4 +A number +Along with the previous setting, this allows you to specify the +coordinate to a pixel representative of the color you want to be +transparent. |